Andybump

[QUOTE=GTB/ZR-1;1607307765]I can't explain that entirely. The have to bring it into the shop. Hook up the computer. They might routinely verify that there are no codes. If you are getting CEL they will verify that code. I do not think a code associated with the exhaust flow control valves takes them directly to the valve learn procedure. So the code might direct them to other procedures that could take time. And, of course, there could actually be another issue. But if there is no code, or an exhaust system related code, my opinion is they should perform the valve learn procedures first, then reset the code(s) if any, and verify they did not return. They should also verify that the valves are moving. So allow 20 minutes for the two procedures, and a generous 40 minutes for bringing it, making the checks, putting on lift to verify valve motion. Approximately and hour - my opinion. I forget - do you have AFM simulators. I do not know if they require a learn - some forum members have reported that learn was not needed with simulator in place of the actual actuators mounted to the muffler.

GTB/ZR-1

***UPDATE***

My buddy has an Autel scanner & was able to get the relearn process—it worked!
Fixed my car, as it’s quieter & the odd V4 harmonic is gone—I’m a happy camper.

Thanks to all for the suggestions, etc—I really appreciate it.

Merry Christmas to all!

combatninja

Glad you got it worked out. Confused what you mean by the "odd V4 harmonic is gone". It is my understanding that the Fabspeed system does not have AFM valves but just uses simulators to spoof the car into thinking they are present. As such, the car will still sound weird when it goes into V4 mode, as all C8 systems do that don't have some way to choke down the flow when it is in that mode.

Andybump

When the car goes into V4 mode, all 4 valves will close on a standard NPP exhaust. So, even though the two AFM valves are not closing (are not there), the tailpipe flow control valves close, forcing the exhaust to flow through the muffler shroud, to the "inner" pair of tail pipes. This likely does sound better/different than when it was in AFM but the tailpipe flow control valves were stuck open.

combatninja

I guess that makes some sense in this case. Still wish all the big name/big money aftermarket exhausts would employ proper AFM valves. I'd never pay $5,000 for an exhaust that is going to sound weird and drone-y intermittently. The AFM on the C8 is pretty dang good and seamless. I'd hate for some funky exhaust notes to ruin the experience. I understand that a lot of others are fine with it but I use my C8 as a daily and I just need everything to work seamlessly. Z-mode or manual mode is fine for the weekend driver but there are times I just need to get in my car, make a phone call and go pick up lunch.

GTB/ZR-1

^^^ Agreed, Andy!